Substrate processing method

ABSTRACT

In a substrate processing method of polishing a periphery of a substrate, in a state where a first polishing surface to which abrasive grains that include particles having a chemical effect on an oxide-silicon-series or nitride-silicon-series film as a main component have been fixed is brought into contact with the periphery of a semiconductor substrate, polishing the periphery of the substrate by sliding the substrate and the first polishing surface. Moreover, in a state where a second polishing surface to which abrasive grains mainly having a mechanical effect have been fixed is brought into contact with the periphery of the substrate, polishing the periphery of the substrate by sliding the substrate and the second polishing surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2007-104068, filed Apr. 11, 2007, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a substrate processing method of polishing the periphery of a semiconductor substrate, and more particularly to a substrate processing method of removing unnecessary films and uneven surfaces formed at the periphery of the substrate.

2. Description of the Related Art

With the recent miniaturization of wiring lines, the concentration values of particles and impurities to be controlled have been getting more severe. Moreover, it has been getting more important to control not only the surface of the semiconductor substrate but also its periphery (including notch parts and bevel parts).

In the manufacturing processes of a semiconductor device, insulating films, such as SiO₂ films or SiN films, and conducting films, such as polysilicon films, W films, or Cu films, are repeatedly subjected to a film forming process, an exposure process, and an etching process, thereby forming microscopic interconnection lines. In the manufacturing processes, not only insulating films and conducting films but also unnecessary films, including insulating films and conducting films, and uneven surfaces are formed at the periphery of the substrate. The unnecessary films and uneven surfaces become the sources of particles in the manufacturing processes and are coming up to the surface as the factor that decreases the yield as a result of miniaturization of interconnection lines.

For example, in the process of making a deep trench in a trench capacitor, a resist pattern is formed on a stacked insulating film obtained by forming an SiN film and an SiO₂ film sequentially by CVD techniques. Then, with the resist pattern as a mask, the SiO₂ film, SiN film, and silicon substrate are etched sequentially by RIE (Reactive Ion Etching) techniques, thereby making a trench. In this case, the generation of plasma and the supply of etching gas become unstable at the periphery of the substrate, with the result that needle-like projections might be formed. The needle-like projections are damaged during the transportation of the substrate or in the course of processing and contribute to the generation of particles. Since such particles lead to a decrease in the yield of manufactured semiconductor devices, it is necessary to remove the needle-like projections formed at the periphery of the substrate.

One method of processing the periphery of the substrate is the technique for sliding a substrate with a surface to be polished and a polishing surface, while pressing the substrate against the polishing surface, thereby polishing and removing the polished film on the substrate. The polishing techniques include the free abrasive grain method and the fixed abrasive grain method. In the free abrasive grain method, the surface to be polished is polished, while an abrading agent including abrasive particles is being supplied to the contact surface between the polishing surface made of nonwoven cloth and the surface to be polished. In the fixed abrasive grain method, the surface to be polished is polished, while purified water is being supplied to the contact surface between the polishing surface to which abrasive grains are fixed and the surface to be polished.

In polishing and removing the needle-like projections caused during the formation of trenches by the fixed grain method, all of the SiN film and needle-like projections on the silicon substrate have been polished and removed using diamond abrasive grains #4000 (with a grain diameter of about 3 μm) which have a high polishing speed. Thereafter, final polishing has been done using diamond abrasive grains #10000 (with a grain diameter of about 0.5 μm). However, with this method, the polishing time has been short, but scratches on the silicon substrate caused by diamond abrasive grains #4000 have been large. Even after final polishing with diamond abrasive grains #10000, scratches have remained (e.g., refer to Jpn. Pat. Appln. KOKAI Publication No. 2003-234314).

To cope with this problem, there has been a method of using diamond abrasive grains #10000 even in polishing and removing the SiN film. However, with this method, it takes an enormous amount of time to polish and remove the SiN film, a high hardness film. As another measure against this problem, there has been a method of decreasing the size of diamond abrasive grains progressively in the order of #4000, #8000, and #10000, thereby improving the finished surface roughness. With this method, however, as many as three kinds of polishing tape are used and therefore three polishing heads are needed, which makes the apparatus larger. Moreover, since the polishing amount of the silicon substrate becomes larger, if a polishing process is carried out a plurality of times in the manufacturing processes of semiconductor devices, the semiconductor devices might depart from the original substrate shape standards and therefore could not be put on the production line.

As described above, the plane roughness of the surface to be polished has to be improved to suppress the occurrence of defects in subsequent processes. The decrease of the size of abrasive grains is effective in improving the plane roughness of the surface to be polished. However, when a high hardness film, such as an SiN film or an SiO₂ film, is polished and removed, a decrease in the abrasive grain size causes the polishing speed to reduce significantly, which produces a side-effect that the productivity might deteriorate.

To increase the polishing removal efficiency without deteriorating the plane roughness of the surface to be polished, the addition of the chemical during polishing has been proposed (e.g., refer to Jpn. Pat. Appln. KOKAI Publication No. 2007-012943). In the proposal, to increase the removal efficiency of the SiN film on a silicon substrate, polyethylenimine or tetramethylammonium hydroxide has been added. However, with this method, since the substrate surface is also exposed to the chemical, a side-effect that the silicon substrate is etched becomes a problem.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided a substrate processing method of polishing a periphery of a substrate, comprising: in a state where a first polishing surface to which abrasive grains that include particles having a chemical effect on an oxide-silicon-series or nitride-silicon-series film as a main component have been fixed is brought into contact with the periphery of a semiconductor substrate, polishing the periphery of the substrate by sliding the substrate and the first polishing surface; and in a state where a second polishing surface to which abrasive grains mainly having a mechanical effect have been fixed is brought into contact with the periphery of the substrate, polishing the periphery of the substrate by sliding the substrate and the second polishing surface.

According to another aspect of the invention, there is provided a substrate processing method of polishing the periphery of a substrate, comprising: polishing the periphery of a semiconductor substrate using a first polishing liquid that includes abrasive grains having a chemical effect on an oxide-silicon-series or nitride-silicon-series film as a main component; and polishing the periphery of the semiconductor substrate using a second polishing liquid that includes abrasive grains mainly having a mechanical effect.

According to still another aspect of the invention, there is provided a substrate processing method of polishing a periphery of a substrate, comprising: polishing the periphery of a semiconductor substrate using fixed or free abrasive grains that include particles having a chemical effect on an oxide-silicon-series or nitride-silicon-series film as a main component; and polishing the periphery of the semiconductor substrate using fixed or free abrasive grains mainly having a mechanical effect.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIGS. 1A and 1B are sectional views to help explain substrate processing steps according to a first embodiment of the invention;

FIG. 2 is a diagram schematically showing the configuration of a fixed-abrasive-grain-type polishing apparatus applied to the first embodiment;

FIGS. 3A and 3B are sectional views to help explain examples of polishing tape used in the polishing apparatus of FIG. 2;

FIG. 4 is a diagram schematically showing the configuration of another fixed-abrasive-grain-type polishing apparatus applied to the first embodiment;

FIGS. 5A to 5C are sectional views to help explain substrate processing steps according to a second embodiment of the invention;

FIGS. 6A to 6D are sectional views to help explain substrate processing steps according to a third embodiment of the invention; and

FIG. 7 is a diagram schematically showing the configuration of a free-abrasive-grain-type polishing apparatus according to a modification of the embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, referring to the accompanying drawings, embodiments of the invention will be explained.

First Embodiment

FIGS. 1A and 1B are sectional views to help explain substrate processing steps according to a first embodiment of the invention. FIG. 1A shows the state of a substrate to be processed before polishing. FIG. 1B shows the state of the substrate after polishing. In FIGS. 1A and 1B, numeral 10 indicates a silicon substrate, 11 an SiO₂ film, and 12 an SiN film.

In the first embodiment, in the structure of FIG. 1A, a first polishing surface to which abrasive grains that include ceria (cerium oxide) having a chemical effect on SiO₂ and SiN as a main component have been fixed is brought into contact with the periphery of the silicon substrate 10. In this state, the substrate 10 is rotated, thereby polishing the substrate periphery. Next, a second polishing surface to which diamond abrasive grains that have mainly a mechanical effect have been fixed is brought into contact with the periphery of the silicon substrate 10. Then, in this state, the substrate 10 is rotated, thereby polishing the substrate periphery. As a result, not only are the SiO₂ film 11 and SiN film 12 removed at the periphery of the substrate 10, but also the surface roughness of the substrate periphery becomes very small.

Hereinafter, the first embodiment will be concretely described.

FIG. 2 is a diagram schematically showing the configuration of a fixed-abrasive-grain-type polishing apparatus applied to the first embodiment.

A stage 21 on which a substrate to be processed 20 is placed can be rotated by a motor 22. The substrate 20 is absorbed and fixed to the stage 21 in such a manner that its center is aligned with the center of the stage 21, with the result that a part of the periphery of the substrate 20 makes contact with a polishing tape 23. A polishing head 24 connected to a cylinder (not shown) presses the polishing tape 23 against the substrate. With the polishing tape 23 being pressed against the periphery of the substrate 20 by the polishing head 24, the motor 22 rotates the substrate 20, thereby polishing the periphery of the substrate 20. Specifically, a part of or all of the unnecessary film formed at the periphery of the substrate 20 is polished and removed until the surface of the substrate 10 has been exposed. During the polishing, purified water is supplied from a nozzle 25 near the center of the substrate to the substrate surface in such a manner that the water is supplied to the polishing area of the substrate periphery.

Two types of polishing tape 23 are used as shown in FIGS. 3A and 3B: one is a first polishing tape 23 a to which abrasive grains that include grains having a chemical effect as a main component have been fixed and the other is a second polishing tape 23 b to which abrasive grains that mainly have a mechanical effect have been fixed. As shown in FIG. 3A, the first polishing tape 23 a is such that ceria abrasive grains 33 (#10000: a grain diameter of about 0.5 μm) are fixed to a PET (polyethylene terephthalate) film 31 with binder 32. The polishing tape 23 a is 80 mm in width and 50 μm in thickness. As shown in FIG. 3B, the second polishing tape 23 b is such that diamond abrasive grains 34 (#10000: a grain diameter of about 0.5 μm) are fixed to a PET film 31 with the binder 32. The width and thickness of the polishing tape 23 b are the same as those of the polishing tape 23 a. These two types of polishing tape 23 can be replaced with each other as needed. Moreover, these polishing tapes 23 are so designed that the part deteriorated as a result of polishing can be replaced with a new polishing surface by rolling up the tape gradually during polishing.

As shown in FIG. 1A, on the entire surface of the silicon substrate 10, a 100-nm-thick SiO₂ film 11 and a 100-nm-thick SiN film 12 were formed sequentially by CVD techniques. The result of applying a polishing method of the first embodiment to the removal of the stacked insulating film formed at the periphery of the substrate 10 will be explained below.

Using the polishing apparatus of FIG. 2, the first polishing tape 23 a to which ceria abrasive grains have been fixed shown in FIG. 3A is set as the polishing tape 23. The substrate to be processed 20 is absorbed and fixed to the stage 21, which is then rotated at a predetermined speed. At the same time, the polishing tape 23 is pressed against the substrate periphery, while the polishing tape 23 is being transported at a predetermined speed, thereby polishing the substrate periphery.

Although the polishing time was twice as long as that of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000, the surface roughness after polishing was ⅕ of that of the combination. Moreover, the polishing time was 1/10 of that of the polishing removal using only the same grain-diameter diamond abrasive grains #10000 and the surface roughness after polishing was about ½ of that of the polishing removal.

On the other hand, when the polishing capability for the silicon substrate 10 is compared in terms of a change in the substrate weight before and after polishing, it is as low as 1/150 of that of diamond abrasive grains #4000 and also as low as ⅕ of that of diamond abrasive grains #10000. These mean that ceria abrasive grains act chemically on the SiO₂ film 11 or SiN film 12 effectively. Furthermore, there is no chemical action on Si, which means that the polishing capability depends on the mechanical strength of the abrasive grains themselves.

When the substrate periphery is polished, since the surface to be polished has a curvature in the cross-sectional direction and circumferential direction of the silicon substrate 10, polishing is performed, while the contact surface of the polishing head 24 is being moved so as to follow the curvature of the silicon substrate 10. At this time, to prevent polishing remains from occurring, excessive polishing is needed. Ceria grains have the advantage of having a high polishing capability for SiO₂ and SiN and a low polishing capability for Si. In the excessive polishing, this advantage works effectively. That is, ceria abrasive grains are very effective in polishing and removing the unnecessary film (SiO₂ film, SiN film) deposited on the periphery of the silicon substrate 10.

As described above, although use of the first polishing tape 23 a to which ceria abrasive grains have been fixed sufficiently reduces the surface roughness after polishing as compared with use of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000, the polishing time gets longer than that of the combination. To overcome this problem, the polishing tape 23 a to which ceria abrasive grains (#10000) have been fixed and the polishing tape 23 b to which diamond abrasive grains (#10000) have been fixed are combined in the first embodiment to shorten the polishing time, which will be explained below.

First, the polishing removal of the stacked insulating film was started with the polishing tape 23 a to which ceria abrasive grains had been fixed and continued until a part of the underlying Si had been exposed. Then, polishing was performed with the polishing tape 23 b to which diamond abrasive grains whose polishing capability for the silicon substrate is higher than that of ceria abrasive grains had been fixed. As a result, the total polishing time was reduced to about ½ of that when only ceria abrasive grains were used. That is, the polishing time became the same as that of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000. At this time, the surface roughness after polishing was reduced to about ⅓ of that of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000.

When the polishing step with the ceria abrasive grain polishing tape 23 a is switched to the polishing step with the diamond abrasive grain polishing tape 23 b or vice versa, the switching between the polishing steps is performed efficiently by using a change in the rotational load of the motor that holds and rotates the substrate to be polished.

Furthermore, instead of polishing with the polishing tape 23 b after the completion of polishing with the polishing tape 23 a, polishing with the polishing tape 23 a was alternated with polishing with the polishing tape 23 b, which produced almost the same effect as described above.

Moreover, as shown in FIG. 4, the polishing tape 23 a to which ceria abrasive grains had been fixed and the polishing tape 23 b to which diamond abrasive grains had been fixed were brought into contact with different places of the periphery of the substrate 20 at the same time, thereby performing polishing with ceria abrasive grains in parallel with polishing with diamond abrasive grains. In this case, the polishing time was reduced to about ⅓ of that when only ceria abrasive grains were used. That is, the polishing time was reduced to ⅔ of that of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000. The surface roughness after polishing was reduced to about ⅓ of the conventional combination.

This means that the removal efficiency of the stacked insulating film was improved by the synergistic effect as a result of the improvement of the polishing efficiency by polishing with ceria abrasive grains whose polishing efficiency was high for the high-hardness SiO₂ film 11 and SiN film 12 and by silicon polishing with diamond abrasive grains after a part of the underlying silicon substrate had been exposed.

As described above, in the first embodiment, the silicon substrate 10 on whose surface the unnecessary film including a high hardness film, including the SiO₂ film 11 and SiN film 12, has been formed is polished using the polishing tape 23 a to which ceria abrasive grains have been fixed and the polishing tape 23 b to which diamond abrasive grains have been fixed. By doing this, not only can the unnecessary film be removed at a high efficiency, but also the polished surface accuracy can be increased. Accordingly, the productivity can be increased and a decrease in the number of defects enables the yield to be improved.

Specifically, a combination of polishing with abrasive grains having a chemical effect and polishing with abrasive grains having a mechanical effect makes it possible not only to remove the unnecessary films, including oxide-silicon-series or nitride-silicon-series high-hardness films, and uneven surfaces at a high efficiency but also to increase the polished surface accuracy.

Furthermore, in place of the stacked film of the SiO₂ film 11 and SiN film, a 200-nm-thick SiO₂ film was formed on the silicon substrate 10 by CVD techniques. At this time, to remove the film on the substrate periphery, the first embodiment was applied using the polishing apparatus of FIG. 4. As a result, a combination of ceria abrasive grains #10000 and diamond abrasive grains #10000 reduced the polishing time to about ½ of that of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000 and further reduced the surface roughness to ⅓ of that of the conventional combination.

Similarly, a 200-nm-thick SiN film was formed on the silicon substrate 10 by CVD techniques. At this time, to remove the film on the substrate periphery, the first embodiment was applied using the polishing apparatus of FIG. 4. As a result, a combination of ceria abrasive grains #10000 and diamond abrasive grains #10000 reduced the polishing time to about ¾ of that of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000 and further reduced the surface roughness to ⅓ of that of the conventional combination.

Second Embodiment

FIGS. 5A to 5C are sectional views to help explain substrate processing steps according to a second embodiment of the invention. FIG. 5A shows a state where trenches are made. FIG. 5B shows a state of a substrate to be processed before polishing. FIG. 5C shows a state of the substrate after polishing. In FIGS. 5A to 5C, numeral 10 indicates a silicon substrate, 11 an SiO₂ film, 12 an SiN film, and 13 needle-like silicon projections.

As shown in FIG. 5A, on the surface of the silicon substrate 10, an SiN film 12 and an SiO₂ film 11 are deposited sequentially by LP-CVD techniques. These films are patterned, thereby forming a hard mask composed of a stacked film of the SiN film 12 and SiO₂ film 11. Then, using the hard mask, the silicon substrate 10 is etched by RIE techniques, thereby making trenches. At this time, etching is disordered at the substrate periphery, with the result that mask remains and needle-like Si projections 13 are formed. Thereafter, the SiO₂ film 11 is peeled by wet etching.

FIG. 5B shows a state where the SiO₂ film 11 has been removed. At the periphery of the silicon substrate 10, an SiN film 12 and needle-like silicon projections 13 have been formed. A polishing method of the second embodiment is applied to the removal of the needle-like silicon projections 13 including the SiN film formed during the formation of trenches and to the planarization of the substrate.

In the second embodiment, too, a polishing method using a combination of the polishing tape 23 a to which ceria abrasive grains #10000 had been fixed and the polishing tape 23 b to which diamond abrasive grains #10000 had been fixed was applied. Using the polishing apparatus of FIG. 4, polishing was performed under predetermined polishing conditions, thereby completing the process as shown in a sectional view of the substrate in FIG. 5C.

Here, when an attempt was made to remove the SiN film 12 and needle-like silicon projections 13 and planarize the substrate 10 only with the ceria-abrasive-grain polishing tape 23 a, even making the polishing time twice as long as that of the conventional combination of diamond abrasive grains #4000 and diamond abrasive grains #10000 failed to finish the removal of the silicon needle-like projections 13. The reason for this is that the removal of the SiN film 12 progressed, but the removal of the silicon needle-like projections 13 and the planarization of the substrate advance slowly.

On the other hand, use of a polishing method using a combination of the ceria-abrasive-grain polishing tape 23 a and the diamond-abrasive-grain polishing tape 23 b reduced the polishing time to ⅔ of the conventional combination, eliminated flaws caused by diamond abrasive grains #4000 observed in the conventional art, and decreased the surface roughness to ⅓ of that of the conventional combination. That is, when the removal of the oxide-silicon-series or nitride-silicon-series unnecessary film and the planarization of the substrate are needed, a combination of the ceria-abrasive-grain polishing tape 23 a and the diamond-abrasive-grain polishing tape 23 b produces a greater effect.

As described above, a substrate to be processed where an SiN film 12 and needle-like silicon projections 13 have been formed at the surface of the silicon substrate 10 is polished using the polishing tape 23 a to which ceria abrasive grains have been fixed and the polishing tape 23 b to which diamond abrasive grains have been fixed, which makes it possible to remove the unnecessary film and needle-like projections 13 at the substrate periphery at a high efficiency and further increase the polished surface accuracy. Accordingly, the same effect as that of the first embodiment is obtained.

Third Embodiment

FIGS. 6A to 6D are sectional views to help explain substrate processing steps according to a third embodiment of the invention.

In the third embodiment, the invention is applied to the removal of metallic contaminants at the substrate periphery caused in forming silicide for a metal film (e.g., Ni or Co).

First, as shown in FIG. 6A, after an SiN film 12 was deposited on the silicon substrate 10, a resist film (not shown) was applied to the SiN film 12. Thereafter, with the resist film as a mask, openings were made to the silicon substrate 10 by photolithography and etching techniques for the SiN film 12.

Next, as shown in FIG. 6B, metal (Co) was deposited by, for example, sputtering techniques, thereby forming a metal film (Co film) 61 on the substrate 10 in the exposed parts from the SiN film 12. Thereafter, the metal film was heat-treated, thereby causing only the surface of the substrate Si exposed in the opening to react with the metal to form a silicide film (CoSi film) 62. The unreacted metal film 61 was removed by etching or the like. At this time, if a resist film were not applied sufficiently to the periphery of the silicon substrate 10, the substrate Si might be exposed at the periphery when openings are made to the silicon substrate 10. If a metal film is deposited on the Si substrate exposed at the periphery and then is heat-treated, Si exposed at the periphery reacts with the metal, producing a reactant of the metal film and Si, such as a silicide film, which causes a problem: metallic contaminants are emitted from the periphery of the silicon substrate 10.

To prevent the emission of metallic contaminants, the metal silicide film 62 and SiN film 12 at the periphery are to be removed after a reactant, such as a silicide film, is formed. As seen from FIG. 6C, the reason why the SiN film 12 at the substrate periphery is removed is that the surrounding SiN film 12 is obstructive to the polishing of the metal silicide film 62 at the substrate periphery. That is, if the SiN film 12 remains around the metal silicide film 62, the metal silicide film 62 cannot be polished efficiently making use of the mechanical effect.

The result of applying the third embodiment to the removal of metallic contaminants developed at the substrate periphery will be explained. The method using the combination of the polishing tape 23 a to which ceria abrasive grains had been fixed and the polishing tape 23 b to which finishing diamond abrasive grains had been fixed in the first embodiment was applied.

Using the polishing apparatus of FIG. 4, a substrate to be processed is absorbed and fixed to the stage 21, which is rotated at a predetermined speed. Then, the polishing tapes 23 (23 a, 23 b) are pressed against the substrate periphery at a predetermined pressure and polish the periphery, while the polishing tapes 23 are being transported at a predetermined speed, thereby bringing the substrate to completion as shown in a sectional view of the substrate in FIG. 6D. In this case, polishing with the polishing tape 23 a having a chemical effect is performed in parallel with polishing with the polishing tape 23 b having a mechanical effect. Accordingly, the SiN film around the metal silicide film to be removed can be polished efficiently, which enables the metal silicide film to be polished and removed reliably.

When polishing was done under the same conditions, the polishing time was reduced to ⅔ of that of the conventional combination of diamond rough abrasive grains (#4000) and finishing abrasive grains (#10000). Moreover, flaws caused by rough diamond abrasive grains observed in the conventional art were eliminated, and the surface roughness was decreased to ⅓ of that of the conventional combination. The reason why the surface roughness was improved is that only finishing diamond abrasive grains were used and rough diamond abrasive grains were not used. Furthermore, the reason why the polishing time was reduced, regardless of using no diamond abrasive grain is that use of the polishing tape 23 a to which ceria abrasive grains had been fixed enabled the SiN film around the metal silicide film at the substrate periphery to be removed efficiently by the chemical effect.

While in the third embodiment, a nitride film (Si nitride film) has been used as a mask material in the third embodiment, an oxide film (Si oxide film) may be used. Even when applied to a case where an oxide film or a nitride film is formed after the formation of silicide to temporarily suppress the metallic contamination of other processes and then not only the silicide film but also the oxide film and nitride film are removed, this produces the effects of reducing the polishing time and improving the surface roughness.

(Modification)

The invention is not limited to the above embodiments. While in the embodiments, SiO₂ and SiN have been used as the unnecessary films at the substrate periphery, the invention is not necessarily restricted to these and may be applied to, for example, SiOC and SiCN. That is, the invention may be applied to oxide-silicon-series and nitride-silicon-series unnecessary films.

When not only an oxide-silicon-series film or a nitride-silicon-series film but also the upper layer, lower layer, or mixed layer of a material difficult to polish with a ceria abrasive grain tape, such as a single-crystal silicon film, an amorphous silicon film, a polysilicon film, or an another silicon series film obtained by introducing impurities into those films, a carbon film, or a metal film (tungsten, copper, aluminum, ruthenium, titanium, tantalum, hafnium, and a compound including those materials) are polished and removed, a combination of the ceria abrasive grains with abrasive grains having a mechanically polishing and removing capability, such as diamond abrasive grains, is effective.

While in the embodiments, ceria particles have been used for an oxide-silicon-series film or a nitride-silicon-series film as abrasive grains having a chemical effect, silica particles may be used instead of ceria particles. Moreover, SiC particles may be used in place of diamond particles.

While in the embodiments, the fixed-abrasive-grain method using polishing tapes has been used in polishing with abrasive grains that include particles having a chemical effect as a main component, a free-abrasive-grain method which performs polishing, while supplying an abrading agent including abrasive particles to the contact surface between the polishing surface and the polished surface may be used instead. Moreover, in polishing by the mechanical effect using diamond abrasive grains, not only the fixed-abrasive-grain method but also free-abrasive-grain method may be used.

Specifically, as shown in FIG. 7, a nonwoven cloth 72 fixed to a polishing head 72 may be brought into contact with the periphery of a substrate to be processed 20 absorbed and fixed to the stage 21 and, at same time, a polishing liquid that includes abrasive grains including ceria grains or the like as a main component may be supplied from a nozzle 73 to the vicinity of the periphery of the substrate 20, thereby causing the substrate periphery to be polished at the part in contact with the nonwoven cloth 72. In this case, too, a combination of polishing with ceria abrasive grains and polishing with diamond abrasive grains produces the same effects as the above embodiments. Here, what is supplied from the nozzle 73 is a polishing liquid that includes abrasive grains including grains having a chemical effect as a main component, not the chemical reacting with the substrate Si. Therefore, the disadvantage of the substrate surface being etched or the like can be avoided.

Furthermore, while in the embodiments, the bevel part, a part where the cross section has a curvature at the end of the semiconductor substrate, has been polished, the invention may be applied to the polishing of a notch part provided at a part of the periphery of the substrate as an alignment mark or for recognizing the crystal orientation on the wafer main surface. Moreover, the semiconductor substrate is not necessarily limited to an Si substrate. Another semiconductor material may be used instead.

Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. 

1. A substrate processing method of polishing a periphery of a substrate, comprising: in a state where a first polishing surface to which abrasive grains that include particles having a chemical effect on an oxide-silicon-series or nitride-silicon-series film as a main component have been fixed is brought into contact with the periphery of a semiconductor substrate, polishing the periphery of the substrate by sliding the substrate and the first polishing surface; and in a state where a second polishing surface to which abrasive grains mainly having a mechanical effect have been fixed is brought into contact with the periphery of the substrate, polishing the periphery of the substrate by sliding the substrate and the second polishing surface.
 2. The substrate processing method according to claim 1, wherein the abrasive grains fixed to the first polishing surface include ceria as a main component and the abrasive grains fixed to the second polishing surface include diamond or SiC as a main component.
 3. The substrate processing method according to claim 1, wherein polishing with the first polishing surface and polishing with the second polishing surface are performed in parallel by rotating the substrate and, at the same time, bringing both the first polishing surface and the second polishing surface into contact with the periphery of the substrate.
 4. The substrate processing method according to claim 1, wherein polishing with the first polishing surface is followed by polishing with the second polishing surface while rotating the substrate.
 5. The substrate processing method according to claim 1, wherein polishing with the first polishing surface and polishing with the second polishing surface are alternately performed while rotating the substrate.
 6. The substrate processing method according to claim 1, wherein the substrate is Si.
 7. The substrate processing method according to claim 1, wherein the periphery of the substrate is a bevel part where the cross section has a curvature at an end of the substrate or a notch part provided on a part of the periphery of the substrate.
 8. The substrate processing method according to claim 1, wherein an unnecessary film and needle-like projections at the periphery of the substrate are removed by polishing with the first polishing surface and by polishing with the second polishing surface.
 9. The substrate processing method according to claim 8, wherein the unnecessary film is SiO₂, SiN, SiOC, or SiCN.
 10. The substrate processing method according to claim 1, wherein an oxide-silicon-series or nitride-silicon-series film and a silicon-series film, a carbon film, a metal film, or metal silicide film at the periphery of the substrate are removed by polishing with the first polishing surface and by polishing with the second polishing surface.
 11. The substrate processing method according to claim 1, wherein the first polishing surface is the surface of a first polishing tape and the second polishing surface is the surface of a second polishing tape and each of the polishing tapes is pressed by a polishing head against the semiconductor substrate.
 12. A substrate processing method of polishing a periphery of a substrate, comprising: polishing the periphery of a semiconductor substrate using a first polishing liquid that includes abrasive grains having a chemical effect on an oxide-silicon-series or nitride-silicon-series film as a main component; and polishing the periphery of the semiconductor substrate using a second polishing liquid that includes abrasive grains mainly having a mechanical effect.
 13. The substrate processing method according to claim 12, wherein the polishing using the first and second polishing liquids is such that a polishing surface is brought into contact with the periphery of the substrate and, at the same time, each of the first and second polishing liquids is supplied to the contact part between the periphery of the substrate and the polishing surface.
 14. The substrate processing method according to claim 12, wherein the first polishing liquid includes abrasive grains having ceria as a main component and the second polishing liquid includes abrasive grains having diamond or SiC as a main component.
 15. The substrate processing method according to claim 12, wherein an unnecessary film and needle-like projections at the periphery of the substrate are removed by polishing with the first polishing liquid and by polishing with the second polishing liquid.
 16. A substrate processing method of polishing a periphery of a substrate, comprising: polishing the periphery of a semiconductor substrate using fixed or free abrasive grains that include particles having a chemical effect on an oxide-silicon-series or nitride-silicon-series film as a main component; and polishing the periphery of the semiconductor substrate using fixed or free abrasive grains mainly having a mechanical effect.
 17. The substrate processing method according to claim 16, wherein the abrasive grains that include particles having a chemical effect as a main component include ceria as a main component and the abrasive grains mainly having a mechanical effect include diamond or SiC as a main component.
 18. The substrate processing method according to claim 17, wherein an unnecessary film and needle-like projections at the periphery of the substrate are removed by polishing with the abrasive grains that include ceria as a main component and by polishing with the abrasive grains that include diamond or SiC as a main component.
 19. The substrate processing method according to claim 16, wherein the substrate is Si.
 20. The substrate processing method according to claim 16, wherein the periphery of the substrate is a bevel part where the cross section has a curvature at an end of the substrate or a notch part provided on a part of the periphery of the substrate. 